Low carbon steel sheet material has been used for many years to make automobile body panels, other body parts, and other vehicle components. Common low carbon steels, without strengthening alloy constituents, are readily shaped in sheet form and readily welded. In an effort to reduce vehicle weight, higher strength steels have been devised so that thinner and lighter steel sheet parts and other lighter steel components could be designed. In many applications it has been difficult to form suitable electrical resistance spot welds in such high strength steel components along with proper quality inspection in a high production rate manufacturing operation.
Repetitive spot welding operations are set-up to form one or more round weld nuggets between assembled high strength steel parts, typically using automated welding equipment. Opposing round electrodes engage opposite sides of the assembly under a controlled set-up force and a controlled welding current is momentarily passed between the electrodes and interposed workpiece to briefly fuse metal at the welding interface. When the current is stopped, the molten metal solidifies to form the familiar round weld nugget of the steel workpiece material.
The welding operation is set-up and often computer controlled to produce a continuous sequence of suitable welds in accordance with specified welding process parameters. It is an object of this invention to provide a method of producing repetitive spot welds in high strength steel alloy workpieces that further facilitates the formation of welded connections in such workpieces.